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Intense habitat-specific fisheries-induced selection at the molecular Pan I locus predicts imminent collapse of a major cod fishery.

Arnason E, Hernandez UB, Kristinsson K - PLoS ONE (2009)

Bottom Line: We hypothesize a potential collapse of the fishery.We find that probabilistic maturation reaction norms for Atlantic cod at Iceland show declining length and age at maturing comparable to changes that preceded the collapse of northern cod at Newfoundland, further supporting the hypothesis.We speculate that immediate establishment of large no-take reserves may help avert collapse.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biology, University of Iceland, Reykjavík, Iceland. einararn@hi.is

ABSTRACT
Predation is a powerful agent in the ecology and evolution of predator and prey. Prey may select multiple habitats whereby different genotypes prefer different habitats. If the predator is also habitat-specific the prey may evolve different habitat occupancy. Drastic changes can occur in the relation of the predator to the evolved prey. Fisheries exert powerful predation and can be a potent evolutionary force. Fisheries-induced selection can lead to phenotypic changes that influence the collapse and recovery of the fishery. However, heritability of the phenotypic traits involved and selection intensities are low suggesting that fisheries-induced evolution occurs at moderate rates at decadal time scales. The Pantophysin I (Pan I) locus in Atlantic cod (Gadus morhua), representing an ancient balanced polymorphism predating the split of cod and its sister species, is under an unusual mix of balancing and directional selection including current selective sweeps. Here we show that Pan I alleles are highly correlated with depth with a gradient of 0.44% allele frequency change per meter. AA fish are shallow-water and BB deep-water adapted in accordance with behavioral studies using data storage tags showing habitat selection by Pan I genotype. AB fish are somewhat intermediate although closer to AA. Furthermore, using a sampling design covering space and time we detect intense habitat-specific fisheries-induced selection against the shallow-water adapted fish with an average 8% allele frequency change per year within year class. Genotypic fitness estimates (0.08, 0.27, 1.00 of AA, AB, and BB respectively) predict rapid disappearance of shallow-water adapted fish. Ecological and evolutionary time scales, therefore, are congruent. We hypothesize a potential collapse of the fishery. We find that probabilistic maturation reaction norms for Atlantic cod at Iceland show declining length and age at maturing comparable to changes that preceded the collapse of northern cod at Newfoundland, further supporting the hypothesis. We speculate that immediate establishment of large no-take reserves may help avert collapse.

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Related in: MedlinePlus

Genotypic frequencies on age in years within year class.Frequencies of AA genotype (red open circles ○, dashed line), AB (magenta pluses +, dotted line), and BB (blue filled circles •, solid line). Lines represent a generalized additive model (gam) smooth fit with quasibinomial link (panel A). Panels B, C and D: gam smooth fit of genotypic frequency on age within year class for the AA, AB and BB genotypes respectively; shaded region represents two standard errors above and below fit. Smooth carries estimated degrees of freedom.
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pone-0005529-g006: Genotypic frequencies on age in years within year class.Frequencies of AA genotype (red open circles ○, dashed line), AB (magenta pluses +, dotted line), and BB (blue filled circles •, solid line). Lines represent a generalized additive model (gam) smooth fit with quasibinomial link (panel A). Panels B, C and D: gam smooth fit of genotypic frequency on age within year class for the AA, AB and BB genotypes respectively; shaded region represents two standard errors above and below fit. Smooth carries estimated degrees of freedom.

Mentions: Genotypic frequencies changed significantly between years within year class (Table 5). Frequency changes can be used to estimate relative fitness of Pan I genotypes. Overall, the genotypic frequencies changed rapidly to about eight years of age (Figure 6) and stayed relatively level after that, an age at which the brunt of fishing of a year class is over. Catch-at-age data show that by eight years of age, a year class is severely reduced and by nine years is almost fished out (Figure S4). Therefore, the selective pressure of the fishery is mostly over by these ages. Taking notice of this fact we took the ratio of the gam predicted frequencies (Figure 6) among 8 year old (post-selection) to 4 year old (entering the fishery) as weights to estimate fitness (Table 6). Relative AA fitness is only 8% and AB 27% showing partial dominance. We used the upper and lower confidence limits to predict best-case and worst-case scenarios. Similar low fitness was obtained using slightly different methods for estimation (Table S2 and Table S3).


Intense habitat-specific fisheries-induced selection at the molecular Pan I locus predicts imminent collapse of a major cod fishery.

Arnason E, Hernandez UB, Kristinsson K - PLoS ONE (2009)

Genotypic frequencies on age in years within year class.Frequencies of AA genotype (red open circles ○, dashed line), AB (magenta pluses +, dotted line), and BB (blue filled circles •, solid line). Lines represent a generalized additive model (gam) smooth fit with quasibinomial link (panel A). Panels B, C and D: gam smooth fit of genotypic frequency on age within year class for the AA, AB and BB genotypes respectively; shaded region represents two standard errors above and below fit. Smooth carries estimated degrees of freedom.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2682699&req=5

pone-0005529-g006: Genotypic frequencies on age in years within year class.Frequencies of AA genotype (red open circles ○, dashed line), AB (magenta pluses +, dotted line), and BB (blue filled circles •, solid line). Lines represent a generalized additive model (gam) smooth fit with quasibinomial link (panel A). Panels B, C and D: gam smooth fit of genotypic frequency on age within year class for the AA, AB and BB genotypes respectively; shaded region represents two standard errors above and below fit. Smooth carries estimated degrees of freedom.
Mentions: Genotypic frequencies changed significantly between years within year class (Table 5). Frequency changes can be used to estimate relative fitness of Pan I genotypes. Overall, the genotypic frequencies changed rapidly to about eight years of age (Figure 6) and stayed relatively level after that, an age at which the brunt of fishing of a year class is over. Catch-at-age data show that by eight years of age, a year class is severely reduced and by nine years is almost fished out (Figure S4). Therefore, the selective pressure of the fishery is mostly over by these ages. Taking notice of this fact we took the ratio of the gam predicted frequencies (Figure 6) among 8 year old (post-selection) to 4 year old (entering the fishery) as weights to estimate fitness (Table 6). Relative AA fitness is only 8% and AB 27% showing partial dominance. We used the upper and lower confidence limits to predict best-case and worst-case scenarios. Similar low fitness was obtained using slightly different methods for estimation (Table S2 and Table S3).

Bottom Line: We hypothesize a potential collapse of the fishery.We find that probabilistic maturation reaction norms for Atlantic cod at Iceland show declining length and age at maturing comparable to changes that preceded the collapse of northern cod at Newfoundland, further supporting the hypothesis.We speculate that immediate establishment of large no-take reserves may help avert collapse.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biology, University of Iceland, Reykjavík, Iceland. einararn@hi.is

ABSTRACT
Predation is a powerful agent in the ecology and evolution of predator and prey. Prey may select multiple habitats whereby different genotypes prefer different habitats. If the predator is also habitat-specific the prey may evolve different habitat occupancy. Drastic changes can occur in the relation of the predator to the evolved prey. Fisheries exert powerful predation and can be a potent evolutionary force. Fisheries-induced selection can lead to phenotypic changes that influence the collapse and recovery of the fishery. However, heritability of the phenotypic traits involved and selection intensities are low suggesting that fisheries-induced evolution occurs at moderate rates at decadal time scales. The Pantophysin I (Pan I) locus in Atlantic cod (Gadus morhua), representing an ancient balanced polymorphism predating the split of cod and its sister species, is under an unusual mix of balancing and directional selection including current selective sweeps. Here we show that Pan I alleles are highly correlated with depth with a gradient of 0.44% allele frequency change per meter. AA fish are shallow-water and BB deep-water adapted in accordance with behavioral studies using data storage tags showing habitat selection by Pan I genotype. AB fish are somewhat intermediate although closer to AA. Furthermore, using a sampling design covering space and time we detect intense habitat-specific fisheries-induced selection against the shallow-water adapted fish with an average 8% allele frequency change per year within year class. Genotypic fitness estimates (0.08, 0.27, 1.00 of AA, AB, and BB respectively) predict rapid disappearance of shallow-water adapted fish. Ecological and evolutionary time scales, therefore, are congruent. We hypothesize a potential collapse of the fishery. We find that probabilistic maturation reaction norms for Atlantic cod at Iceland show declining length and age at maturing comparable to changes that preceded the collapse of northern cod at Newfoundland, further supporting the hypothesis. We speculate that immediate establishment of large no-take reserves may help avert collapse.

Show MeSH
Related in: MedlinePlus